cooling for newborns with hypoxic ischaemic encephalopathy

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Cooling for newborns with hypoxic ischaemic encephalopathy

(Review)

Jacobs SE, Hunt R, Tarnow-Mordi WO, Inder TE, Davis PG

This is a reprint of a Cochrane review, prepared and maintained by The Cochrane Collaboration and published in The Cochrane Library2008, Issue 4

http://www.thecochranelibrary.com

Cooling for newborns with hypoxic ischaemic encephalopathy (Review)

Copyright 2008 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
http://www.thecochranelibrary.com/http://www.thecochranelibrary.com/


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T A B L E O F C O N T E N T S

1HEADER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2PLAIN LANGUAGE SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2BACKGROUND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3OBJECTIVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4METHODS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5RESULTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12 AUTHORS CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12 ACKNOWLEDGEMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15CHARACTERISTICS OF STUDIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

25DATA AND ANALYSES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Analysis 1.1. Comparison 1 Therapeutic hypothermia versus standard care, Outcome 1 Death or major disability in

survivors assessed, by quality of follow-up. . . . . . . . . . . . . . . . . . . . . . . . . 28

Analysis 1.2. Comparison 1 Therapeutic hypothermia versus standard care, Outcome 2 Death or major disability in

survivors assessed, by method of cooling. . . . . . . . . . . . . . . . . . . . . . . . . 29

Analysis 1.3. Comparison 1 Therapeutic hypothermia versus standard care, Outcome 3 Mortality, by method of cooling. 30

Analysis 1.4. Comparison 1 Therapeutic hypothermia versus standard care, Outcome 4 Major neurodevelopmental

disability, by quality of follow-up. . . . . . . . . . . . . . . . . . . . . . . . . . . . 31


disability in survivors assessed, by quality of follow-up. . . . . . . . . . . . . . . . . . . . . 32


disability in survivors assessed, by method of cooling. . . . . . . . . . . . . . . . . . . . . 33

Analysis 1.7. Comparison 1 Therapeutic hypothermia versus standard care, Outcome 7 Cerebral palsy in survivors assessed,

by method of cooling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34Analysis 1.8. Comparison 1 Therapeutic hypothermia versus standard care, Outcome 8 Neuromotor delay (BSID PDI

more than 2 SD below mean) in survivors assessed, by quality of follow-up. . . . . . . . . . . . . 35

Analysis 1.9. Comparison 1 Therapeutic hypothermia versus standard care, Outcome 9 Neuromotor delay (BSID PDI

more than 2 SD below mean) in survivors assessed, by method of cooling. . . . . . . . . . . . . . 36

Analysis 1.10. Comparison 1 Therapeutic hypothermia versus standard care, Outcome 10 Neuromotor development (BSID

PDI) in survivors assessed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Analysis 1.11. Comparison 1 Therapeutic hypothermia versus standard care, Outcome 11 Developmental delay (BSID

MDI more than 2 SD below mean) in survivors assessed, by quality of follow-up. . . . . . . . . . . 37

Analysis 1.12. Comparison 1 Therapeutic hypothermia versus standard care, Outcome 12 Developmental delay (BSID

MDI more than 2 SD below mean) in survivors assessed, by method of cooling. . . . . . . . . . . . 38

Analysis 1.13. Comparison 1 Therapeutic hypothermia versus standard care, Outcome 13 Mental development (BSID

MDI) in survivors assessed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Analysis 1.14. Comparison 1 Therapeutic hypothermia versus standard care, Outcome 14 Blindness in survivors assessed,by method of cooling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Analysis 1.15. Comparison 1 Therapeutic hypothermia versus standard care, Outcome 15 Deafness in survivors assessed,

by method of cooling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Analysis 1.16. Comparison 1 Therapeutic hypothermia versus standard care, Outcome 16 Sinus bradycardia. . . . 42

Analysis 1.17. Comparison 1 Therapeutic hypothermia versus standard care, Outcome 17 Hypotension requiring inotropic

support. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Analysis 1.18. Comparison 1 Therapeutic hypothermia versus standard care, Outcome 18 Arrhythmia requiring medical

treatment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Analysis 1.19. Comparison 1 Therapeutic hypothermia versus standard care, Outcome 19 Anaemia requirning

transfusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Analysis 1.20. Comparison 1 Therapeutic hypothermia versus standard care, Outcome 20 Leukopaenia. . . . . . 45

Analysis 1.21. Comparison 1 Therapeutic hypothermia versus standard care, Outcome 21 Thrombocytopaenia. . . 46

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Analysis 1.22. Comparison 1 Therapeutic hypothermia versus standard care, Outcome 22 Coagulopathy resulting in major

thrombosis or haemorrhage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 Analysis 1.23. Comparison 1 Therapeutic hypothermia versus standard care, Outcome 23 Hypoglycaemia. . . . . 47

Analysis 1.24. Comparison 1 Therapeutic hypothermia versus standard care, Outcome 24 Hypokalaemia. . . . . 48

Analysis 1.25. Comparison 1 Therapeutic hypothermia versus standard care, Outcome 25 Oliguria. . . . . . . 48

Analysis 1.26. Comparison 1 Therapeutic hypothermia versus standard care, Outcome 26 Sepsis. . . . . . . . 49

Analysis 1.27. Comparison 1 Therapeutic hypothermia versus standard care, Outcome 27 Seizures. . . . . . . 49

Analysis 2.1. Comparison 2 Therapeutic hypothermia versus standard care in infants with severe encephalopathy, Outcome

1 Death or major disability in survivors assessed. . . . . . . . . . . . . . . . . . . . . . . 50


2 Mortality. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51


3 Major disability in survivors assessed. . . . . . . . . . . . . . . . . . . . . . . . . . 51

Analysis 3.1. Comparison 3 Therapeutic hypothermia versus standard care in infants with moderate encephalopathy,

Outcome 1 Death or major disability in survivors assessed. . . . . . . . . . . . . . . . . . . 52Analysis 3.2. Comparison 3 Therapeutic hypothermia versus standard care in infants with moderate encephalopathy,

Outcome 2 Mortality. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Analysis 3.3. Comparison 3 Therapeutic hypothermia versus standard care in infants with moderate encephalopathy,

Outcome 3 Major disability in survivors assessed. . . . . . . . . . . . . . . . . . . . . . 53

53WHATS NEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

53HISTORY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

54CONTRIBUTIONS OF AUTHORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

54DECLARATIONS OF INTEREST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

55SOURCES OF SUPPORT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

55INDEX TERMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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[Intervention Review]


Susan E Jacobs1 , Rod Hunt2, William O Tarnow-Mordi3 , Terrie E Inder4, Peter G Davis5

1Neonatal Services, Royal Womens Hospital, Carlton, Melbourne, Australia. 2Department of Neonatal Medicine, Royal Childrens

Hospitals, Melbourne, Parkville, Melbourne, Australia. 3Department of Neonatal Medicine, Westmead Hospital, Westmead, Australia.4Departments of Pediatrics, Neurology and Radiology, St. Louis Childrens Hospital, Washington University, St. Louis, MO, USA.5Department of Obstetrics and Gynaecology, Royal Womens Hospital, Carlton, Australia

Contact address: Susan E Jacobs, Neonatal Services, Royal Womens Hospital, 132 Grattan Street, Carlton, Melbourne, Victoria, 3953,

Australia. [email protected].

Editorial group: Cochrane Neonatal Group.

Publication status and date: Edited (no change to conclusions), published in Issue 4, 2008.

Review content assessed as up-to-date: 27 June 2007.

Citation: Jacobs SE, Hunt R, Tarnow-Mordi WO, Inder TE, Davis PG. Cooling for newborns with hypoxic ischaemicencephalopathy.

Cochrane Database of Systematic Reviews2007, Issue 4. Art. No.: CD003311. DOI: 10.1002/14651858.CD003311.pub2.


A B S T R A C T

Background

Newborn animal studies and pilot studies in humans suggest that mild hypothermia following peripartum hypoxia-ischaemia in

newborn infants may reduce neurological sequelae without adverse effects.

Objectives

To determine the effect of therapeutic hypothermia in encephalopathic asphyxiated newborn infants on mortality, long-term neurode-

velopmental disability and clinically important side effects.

Search strategy

The standard search strategy of the Neonatal Review Group as outlined in The Cochrane Library (Issue 2, 2007) was used. Randomised

controlled trials evaluating therapeutic hypothermia in term newborns with hypoxic ischaemic encephalopathy were identified by

searching the Oxford Database of Perinatal Trials, the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane

Library, Issue 2, 2007), MEDLINE (1966 to June 2007), previous reviews including cross-references, abstracts, conferences, symposiaproceedings, expert informants and journal hand searching.

Selection criteria

Randomised controlled trials comparing the use of therapeutic hypothermia with standard care in encephalopathic newborn infants

with evidence of peripartum asphyxia and without recognisable major congenital anomalies were included. The primary outcome

measure was death or long-term major neurodevelopmental disability. Other outcomes included adverse effects of cooling and early

indicators of neurodevelopmental outcome.

Data collection and analysis

Threereview authors independently selected, assessed the quality of and extracted datafrom the included studies. Authors werecontacted

for further information. Meta-analyses were performed using relative risk and risk difference for dichotomous data, and weighted mean

difference for continuous data with 95% confidence intervals.

1Cooling for newborns with hypoxic ischaemic encephalopathy (Review)

mailto:[email protected]:[email protected]


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Main results

Eight randomised controlled trials were included in this review, comprising 638 term infants with moderate/ severe encephalopathy

and evidence of intrapartum asphyxia. Therapeutic hypothermia resulted in a statistically significant and clinically important reduction

in the combined outcome of mortality or major neurodevelopmental disability to 18 months of age [typical RR 0.76 (95% CI 0.65,

0.89), typical RD -0.15 (95% CI -0.24, -0.07), NNT 7 (95% CI 4, 14)]. Cooling also resulted in statistically significant reductions

in mortality [typical RR 0.74 (95% CI 0.58, 0.94), typical RD -0.09 (95% CI -0.16, -0.02), NNT 11 (95% CI 6, 50)] and in

neurodevelopmental disability in survivors [typical RR 0.68 (95% CI 0.51, 0.92), typical RD -0.13 (95% CI -0.23, -0.03)]. Some

adverse effects of hypothermia included an increase in the need for inotrope support of borderline significance and a significant increase

in thrombocytopaenia.

Authors conclusions

There is evidence from the eight randomised controlled trials included in this systematic review (n = 638) that therapeutic hypothermia

is beneficial to term newborns with hypoxic ischaemic encephalopathy. Cooling reduces mortality without increasing major disability

in survivors. The benefits of cooling on survival and neurodevelopment outweigh the short-term adverse effects. However, this reviewcomprises an analysis based on less than half of all infants currently known to be randomised into eligible trials of cooling. Incorporation

of data from ongoing and completed randomised trials (n = 829) will be important to clarify the effectiveness of cooling and to provide

more information on the safety of therapeutic hypothermia, but could also alter these conclusions. Further trials to determine the

appropriate method of providing therapeutic hypothermia, including comparison of whole body with selective head cooling with mild

systemic hypothermia, are required.

P L A I N L A N G U A G E S U M M A R Y


There is evidence that induced hypothermia (cooling) of newborn babies who may have suffered from a lack of oxygen at birth reducesdeath or disability, without increasing disability in survivors. This means that parents should expect that cooling will decrease their

babys chance of dying, and that if their baby survives, cooling will decrease his/her chance of major disability. A lack of oxygen before

and during birth can destroy cells in a newborn babys brain. The damage caused by the lack of oxygen continues for some time

afterwards. One way to try and stop this damage is to induce hypothermia - cooling the baby or just the babys head for hours to days.

This treatment may reduce the amount of damage to brain cells. This review found that there is evidence from trials to show that

induced hypothermia helps to improve survival and development at 18 months for term newborn babies at risk of brain damage. The

results of ongoing trials may or may not confirm these favourable results. More research is also needed on the different methods of

cooling.

B A C K G R O U N D

In technically developed countries, peripartum asphyxia affects 3 -

5 per 1000 live births with subsequent moderate or severe hypoxic

ischaemic encephalopathy (HIE) in 0.5 - 1 per 1000 live births

(Levene 1986). HIE is a major problem worldwide as 10 - 60%

of affected infants die, and at least 25% of survivors have long-

term neurodevelopmental sequelae (Vannucci 1990).There are no

specific treatments proven to decrease brain damage from HIE.

Hypothermia is a clinically feasible manoeuvre that may improve

the outcome of neonates with HIE.

Recent clinical and experimental studies have demonstrated that

neuronal deathoccursin twophases followinga reversiblehypoxic-

ischaemic global insult (Gluckman 1992; Lorek 1994; Penrice

1996). If the insult is severe, there may be immediate primary

neuronal death related to cellular hypoxia with exhaustion of the

cells high energy stores (primary energy failure). After a latent pe-

riod of at least six hours, the secondary phase of delayed neuronal

death begins (Williams 1991). The mechanisms involved in de-

layed neuronal death include hyperaemia, cytotoxic oedema, mi-

tochondrial failure, accumulation of excitotoxins, active cell death

(analogous to developmental apoptosis), nitric oxide synthesis, free

radical damage and cytotoxic actions of activated microglia (Inder




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2000). The delayed phase is associated with encephalopathy and

increased seizure activity, and accounts for a significant proportionof the final cell loss even after very severe insults.

In term infants with evidence of intrapartum hypoxia and mod-

erate to severe encephalopathy, magnetic resonance spectroscopy

studies are consistent with this biphasic model of neuronal death.

These studies demonstrate normal cerebral oxidative metabolism

shortly after birth followed by secondary energy failure, the de-

gree of which predicts outcome (mortality and neurodevelopmen-

tal outcome at both one and four years of age) (Roth 1997; Roth

1992). Therefore, a therapeutic window of opportunity exists in

the interval following resuscitation of the asphyxiated newborn

before the secondary phase of impaired energy metabolism and

injury.There are a number of postulated mechanisms by which hypother-

mia may be neuroprotective. Hypothermia may modify cells pro-

grammed for apoptosis, leading to their survival. In neonatal

piglets, 12 hours of mild hypothermia after resuscitation signifi-

cantly decreased the number of apoptotic cells, but not the num-

ber of necrotic cells (Edwards 1995). Hypothermia may also pro-

tect neurons by reducing cerebral metabolic rate, attenuating the

release of excitatory amino acids (glutamate, dopamine), amelio-

rating the ischaemia-impaired uptake of glutamate and lowering

production of toxic nitric oxide and free radicals (Globus 1995).

Several term and preterm animal experimental models have

demonstrated that a reduction in brain temperature of 2 - 3 de-grees Celsius immediately following a hypoxic-ischaemic insult

reduces energy expenditure, improves subsequent performance

testing and/or reduces histological neuronal loss (Laptook 1994;

Laptook 1997; Thoresen 1995; Gunn 2001). In the term fetal

lamb, a significant reduction in histological neuronal loss was seen

with extradural temperatures below 35 degrees Celsius (Gunn

1997a). Temperature modelling calculations also suggest that low-

ering an infants core temperature to below 35 degrees Celsius is

required to produce any reduction in the deep brain temperature

(Van Leeuwen 2000).

For many decades, deep hypothermia to less than 28 degrees Cel-

sius has been shown to be valuable for neuroprotection duringcar-

diac arrest for open-heart and neurosurgical procedures. There are

three Cochrane systematic reviews of the effect of systemic cool-

ing on outcome of human adults following head injury (Alderson

2004), acute stroke (Correia 1999) and coronary artery bypass

surgery (Rees 2001). There is currently no evidence from ran-

domised controlled trials or these systematic reviews to support

the use of hypothermia for treatment of either head injury or

acute stroke, or for prevention of neurological injury aftercoronary

artery bypass surgery. In addition, hypothermia may be harmful

by increasing the risk of sepsis (Alderson 2004), as well as periop-

erative myocardial dysfunction and mortality (Rees 2001).

Mild hypothermia appears to be well tolerated in a variety of

experimental animal models, as well as in adult human studies

(Gunn 1997b, Thoresen 1995; Thoresen 1996; Haaland 1997;Marion 1997). There were no reported serious adverse effects in

four pilot studies of hypothermia in human newborns (Gunn

1998;Azzopardi2000; Thoresen 2000; Shankaran2002). Adverse

effects, such as sinus bradycardia, increased blood pressure and in-

creased oxygen requirement, were all transient and reversible with

rewarming (Thoresen 2000).

Therapeutic hypothermia aims to lower the temperature of the

vulnerable deep brain structures, the basal ganglia, to 32 - 34 de-

grees Celsius. Two methods are being evaluated in newborn in-

fants with HIE: whole body cooling and selective head cooling

with mild systemic hypothermia. The rationale for selective head

cooling is that the newborn infants brain produces 70% of totalbody heat and that systemic hypothermia may be physiologically

harmful to the sick neonate. Therefore, the adverse effects of sys-

temic cooling may be minimised by selectively cooling the brain

more than the body (Gunn 1998). However, a theoretical mod-

elling of cooling investigating temperature distribution within the

neonatal head found that the only situation that resulted in a sig-

nificant reduction in deep brain temperature was when the core

body temperature was lowered to 34 degrees Celsius, implying

that it is necessary to reduce systemic temperature to achieve deep

brain cooling (Van Leeuwen 2000). Whole body cooling relies on

core body and deep brain temperatures being similar.

Identification of infants with hypoxic-ischaemic brain injury at

risk of future disability who maybenefit from hypothermia is chal-

lenging. It may be particularly difficult to distinguish between en-

cephalopathy secondary to intrapartum hypoxia and that related

to antepartum factors (Badawi 1998a; Badawi 1998b) or underly-

ing congenital abnormalities not easily recognisable at birth (Felix

2000). Recent newborn animal and adult human studies are con-

sistent with the potential for rescue hypothermia being greatest

following moderate, rather than severe, hypoxic-ischaemic insults

(Marion 1997; Haaland 1997). Aspects of cooling therapy that

remain controversial include: how soon after the insult or birth

does cooling need to be started, what level of hypothermia is re-

quired, what method (selective head cooling vs. whole body cool-ing) should be used and what is the duration of cooling required.

Effective therapies are urgently required to prevent neurosensory

impairment following peripartum asphyxia. This systematic re-

view reviews the evidence to determine whether therapeutic hy-

pothermia reduces adverse outcome in encephalopathic asphyxi-

ated newborn infants.

O B J E C T I V E S

To determine the effect of therapeutic hypothermia on death and




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long-term neurodevelopmental disability, and to ascertain clini-

cally important side effects in newborn infants with HIE.

Secondary objectives include assessment of the adverse effects of

cooling and effects on early prognostic indicators of adverse out-

come. Subgroup analyses were planned on the basis of:

1. Severity of HIE (mild, moderate, severe) (Sarnat 1976; Finer

1981)

2. Inclusion criteria:

a) Preterm (< 35 weeks gestation) vs. term or near-term (> 35

weeks gestation)

b) Electrophysiological plus clinical criteria vs. clinical criteria

alone

3. Timing of commencement of intervention (< 3 hours vs. 3 - 6

hours vs. > 6 hours)

4. Method of cooling (whole body vs. selective head cooling with

mild systemic hypothermia)

5. Degree of cooling [core temperature (or surrogate eg rectal tem-

perature) < 34.5 vs. > 34.5 degrees Celsius]

6. Duration of cooling (< 48 hours vs. > 48 hours)

7. Quality of outcome assessment [high quality (> 18 months

with formal psychological testing and review by developmental

paediatrician for diagnosis of cerebral palsy) vs. lower quality].

M E T H O D S

Criteria for considering studies for this review

Types of studies

All randomised and quasi-randomised studies comparing the use

of therapeutic hypothermia with standard care were included.

Types of participants

1. Newborn infants

2. Evidence of peripartum asphyxia, with each enrolled infant

satisfying at least one of the following criteria:

a) Apgar score of 5 or less at 10 minutes

b) Mechanical ventilation or resuscitation at 10 minutes

c) Cord pH < 7.1, or an arterial pH < 7.1 or base deficit of 12 or

more within 60 minutes of birth

3. Evidence of encephalopathy according to Sarnat staging (Sarnat

1976; Finer 1981):

a) Stage 1 (Mild): hyperalertness, hyper-reflexia, dilated pupils,

tachycardia, absence of seizures.

b) Stage 2 (Moderate): lethargy, hyper-reflexia, miosis, bradycar-

dia, seizures, hypotonia with weak suck and Moro.c) Stage 3 (Severe): stupor, flaccidity, small to midposition pupils

which react poorly to light, decreasedstretch reflexes, hypothermia

and absent Moro.

4. No major congenital abnormalities recognisable at birth

Types of interventions

Cooling (whole body or selective head cooling) vs. no cooling

(standard care).

Types of outcome measures

The primary outcome measure was death or long-term (> 18months) major neurodevelopmental disability [cerebral palsy, de-

velopmental delay (Bayley or Griffith assessment more than 2 SD

below the mean) or intellectual impairment (IQ more than 2 SD

below mean), blindness (vision < 6/60 in both eyes), sensorineural

deafness requiring amplification].

Secondary outcomes included:

1. Each component of the primary outcome:

a) Mortality

b) Major neurodevelopmental disability

c) Cerebral palsy

d) Developmental delay or intellectual impairment

e) Blindness

f) Sensorineural deafness requiring amplification2. The incidence of adverse effects of cooling:

a) Heart rate

i) Sinus bradycardia (heart rate < 80/minute)

ii) Prolonged QT interval

iii) Arrhythmia requiring medical intervention and/or cessation of

cooling

b) Blood pressure

i) Hypotension (mean arterial pressure < 40 mmHg)

ii) Need for inotrope support

c) Full blood examination

i) Anaemia (Hb 2 mmol/L)

h) Renal impairment

i) Urea (maximum mean SD)

ii) Creatinine (maximum mean SD)

iii) Oliguria (less than 1 ml/kg/hour)

i) Culture proven sepsis (positive blood, CSF or bladder tap urine

culture)




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3. Early indicators of neurodevelopmental outcome:

a) Severity of encephalopathy (Sarnat staging) (Sarnat 1976; Finer1981)

b) Severity of electroencephalogram (EEG) abnormality:

i) Severe: isoelectric or burst-suppression pattern

ii) Moderate: low voltage or discontinuous background

iii) Mild: electrographic seizures, dysmaturity

c) Seizures (and number of anticonvulsants)

d) Diffusion weighted imaging (DWI) on early MRI (< day 4)

e) Basal ganglia, posterior limb of internal capsule (PLIC) and/or

white matter (WM) injury, parasagittal neuronal necrosis on late

MRI (> day 4).

f ) Standardised neurological assessment day seven (Dubowitz

1998)

g) Days to full sucking feeds

Search methods for identification of studies

The standard search strategy of the Neonatal Review Group as

outlined in The Cochrane Library (Issue 2, 2007) was used. This

included searches of the Oxford Database of Perinatal Trials, the

Cochrane Central Register of Controlled Trials (CENTRAL, The

Cochrane Library, Issue 2, 2007), MEDLINE {Silver Platter -

1966 to June, 2007: Infant, Newborn (explode) [MeSH heading]

and Asphyxia (explode) [MeSH heading] or Hypoxic Ischaemic

Encephalopathy and Hypothermia (explode) [MeSH heading]},

previous reviews including cross-references, abstracts, conferences,symposia proceedings, expertinformants and journal hand search-

ing. No language restrictions were applied.

Data collection and analysis

This systematic review followed the Cochrane Collaboration

methodology according to guidelines of the Neonatal Review

Group. Three review authors independently identified the studies

to be included, assessed the quality of the studies and extracted the

data. Methodological quality assessment was based on 1) blinding

of randomisation, 2) blinding of intervention, 3) completeness of

follow-up and 4) blinding of outcome measurement. When nec-essary, additional information and clarification of published data

was requested from the authors of individual trials. Meta-anal-

yses were performed using the fixed effects model. Relative risk

(RR) and risk difference (RD) were calculated for dichotomous

data and weighted mean difference (WMD) for continuous data,

with 95% confidence intervals (CI) for all analyses. The number

needed to treat (NNT) and associated 95% CI were determined

for a statistically significant reduction in the RD. Heterogeneity

was examined using the I squared test.

Outcome data are reported and analysed in this review for all

randomised participants with known outcomes. Those with miss-

ing outcome data are excluded from analysis. For the primary

outcome, death or major disability, a sensitivity analysis was per-

formed to allow for the additional uncertainty arising from miss-ing outcome data (Gamble 2005).

R E S U L T S

Description of studies

See: Characteristics of includedstudies; Characteristicsof excluded

studies; Characteristics of ongoing studies.

Eight randomised controlled trials met inclusioncriteria for thisre-view(Gunn1998; Shankaran2002; ICE2002;Akisu 2003; Eicher

2005; Gluckman 2005; Shankaran 2005; Lin 2006). Six were

performed as pilot studies, three in single centres [New Zealand

(Gunn 1998), Turkey (Akisu 2003) and China (Lin 2006)] and

the others at multiple centres in Australia (ICE 2002) and North

America (Shankaran 2002; Eicher 2005). Two large multicentred

randomised controlled trials have been published, one interna-

tional (Gluckman 2005) and the otherfrom theNICHDnetwork

in North America (Shankaran 2005).

All eight trials included term newborn infants with moderate or

severe encephalopathy and evidence of intrapartum hypoxia-is-

chaemia without obvious congenital abnormalities.

Infants in all studies were randomised with initiation of the in-tervention by six hours of age [mean age at entry range: 1.9

hours (Akisu 2003) to 4.6 hours (Gluckman 2005)]. Four stud-

ies used head cooling devices in conjunction with whole body

cooling (Gunn 1998; Akisu 2003; Gluckman 2005; Lin 2006),

while the other four used whole body cooling alone (Shankaran

2002; ICE 2002; Eicher 2005; Shankaran 2005). The duration

of hypothermia was 72 hours in all but one study that cooled in-

fants for 48 hours (Eicher 2005). Six studies rewarmed infants by

0.5 degrees Celsius per hour with the rewarming period of four

hours (Akisu 2003; Eicher 2005; Gluckman 2005; Gunn 1998;

Shankaran 2002; Shankaran 2005), one study rewarmed infants

by 0.5 degrees Celsius every second hour with a duration of 8

hours for rewarming (ICE 2002) and one study allowed infants torewarm spontaneously at room temperature, such that rewarming

took up to 12 hours (Lin 2006).

Mortality was ascertained up to latest follow-up in all studies,

ranging from 10 days of age (Lin 2006), to hospital discharge

(Shankaran 2002; ICE 2002; Akisu 2003) or to neurodevelop-

mental assessment at 12 months (Eicher 2005) or 18 - 22 months

(Gunn 1998; Gluckman 2005; Shankaran 2005). Decisions to

withdraw care were reported to precede death in five trials (ICE

2002, Shankaran 2002, Eicher 2005, Shankaran 2005, Lin 2006).

Gunn, Gluckman and Shankaran (2005) presented short and

long-term outcomes to 18 - 22 months, but Shankaran (2002),

ICE, Akisu and Lin reported short-term morbidity to 10 days of




9/58

age or discharge from hospital. Eicher reported both short-term

morbidity and 12 month neuromotor outcome.One trial reported industry sponsorship (Gluckman 2005);

Olympic Medical (Seattle, WA, USA) provided financial and ad-

ministrative support and equipment and monitored data for accu-

racy but was not involved in study design, data interpretation or

publication. In the other included studies, there was no disclosure

of sponsorship from industry.

Gunn 1998 reported the short-term medical outcomes of 22 term

infants with hypoxic ischaemic encephalopathy (10 controls ran-

domized to normothermia and 12 randomised to hypothermia)

in a randomised controlled pilot study (Gunn 1998). The first six

randomised hypothermic infants received minimal cooling (36.0

- 36.5C, n = 6) and then the next six mild cooling (35.5 - 35.9C,

n = 6) as part of this safety study. The study continued and the18 month outcome of these 22 infants, together with a further

18 infants [nine randomised (three normothermic controls, with

six allocated to hypothermia to 34.5 - 35.4C) and nine non-ran-

domised (two controls, seven cooled to 34 - 35C)] were reported

in a subsequent publication (Battin 2001). The combined results

of the 31 randomised infants (13 normothermic controls, 18 al-

located to hypothermia) are presented (Gunn 1998), with indi-

vidual patient data provided by the authors. The non-randomised

patients were not included in this review. There was one further

report of short-term medical outcomes arising from these studies

that included the 13 randomised control infants with six infants

randomised to 34.5 - 35.4C and the seven non-randomised in-

fants at 34 - 35C (Battin 2003). For the purpose of this systematicreview, all randomised infants in the various reports (Gunn 1998;

Battin 2001; Battin 2003) are included in the study referred to as

Gunn 1998. This study did not report whether any infants had

treatment withdrawn prior to death. Eighteen month neurode-

velopmental outcome assessment using the BSID was performed

by a psychologist blinded to treatment allocation. Neurodevelop-

mental outcomes were determined from Table 2 in Battin 2001,

and comprised randomised infants (normothermia, numbers 1 -

13; hypothermia, numbers 16 - 33) ascertained from the author.

Adverse neurodevelopmental outcome was defined byGunn 1998

as BSID MDI or PDI < 70.

Shankaran 2002 reported the short-term medical outcomes to

hospital discharge of 19 term infants with peripartum asphyxiaandeither seizuresor moderate/ severe encephalopathy (Shankaran

2002). There were 10 controls and nine infants randomised to

34.5Cby meansof a servo-controlled coolingblanket. Withdrawal

of care preceded three of five deaths (2/2 cooled and 1/3 standard

care).

ICE 2002 reported short-term morbidity to hospital discharge of

17 near-term infants with moderate or severe encephalopathy and

intrapartum hypoxia-ischemia with two of the following criteria:

Apgarscore < 5 at 10 minutes, ongoing resuscitation with the need

for ventilation at 10 minutes, cord or arterial blood gas within

one hour of birth with pH < 7.1 and/or base deficit in excess of

12. Infants were excluded if they had congenital abnormalities,

weighed < 2000 grams, required > 0.8 FiO2 or were consideredto be in extremis with death imminent (ICE 2002). Decisions to

withdraw life support preceded all 4 deaths.

Akisu 2003reported the short-termmedicaloutcomesto discharge

from hospital of 21 term infants with peripartum asphyxia and

encephalopathy defined as stupor, hypotonia or abnormal neona-

tal reflexes. Eleven infants had their temperature lowered by cool-

ing caps with cold water at 5 - 10C placed around the scalp for

72 hours. The left external auditory canal and rectal temperatures

were monitored to maintain the external auditory canal tempera-

ture at 33 - 33.5C with the rectal temperature at 36 - 36.5C with

the servo-mechanism of the radiant warmer. Ten control infants

had their rectal temperature maintained at 36 - 36.5C with the

servo-mechanismof radiant warmer.An additional sevennon-ran-domised term control infants without asphyxia were not included

in this review (Akisu 2003). Decisions to withdraw care were not

reported.

In two consecutive publications, Eicher 2005 reported in-hospi-

tal morbidity with mortality and neurodevelopmental outcomes

to 12 months of age in 53/65 (81.5%) near-term infants with

peripartum hypoxia-ischaemia and encephalopathy (two of: pos-

turing, seizures, autonomic dysfunction, or abnormalities of tone,

reflexes or state of consciousness). Thirty-two infants had their

temperature lowered by the initial application of ice to head and

body for upto two hours thatwas then maintained at32.5- 33.5C

(rectal)on a servo-controlled cooling blanket for48 hours.Thirty-

three control infants had their rectal temperature maintained at36.5 - 37.5C by servo-controlled radiant warmer (Eicher 2005).

Eighteen of 24 deaths were preceded by withdrawal of care (9/

10 cooled and 9/14 standard care). Neurodevelopmental outcome

was assessed using the BSID, CAT/CLAMS or Vineland exami-

nations at 12 months of age by the developmental team blinded to

study group assignment. Severe neuromotor disability was defined

by Eicher 2005 as BSID PDI < 70. This study was considered

to be of lower quality because the neurodevelopmental outcome

assessment was at 12 months rather than 18 - 24 months.

Gluckman 2005 reported mortality and severe neuromotor dis-

ability to 18 months of age in 218/234 (93%) near-term in-

fants born with evidence of peripartum hypoxia-ischaemia, mod-

erate or severe encephalopathy or clinical seizures and moderateor severely abnormal background or seizures on amplitude inte-

grated electroencephalography. One hundred and sixteen infants

had their temperature lowered by head cooling by cooling cap

(Olympic Medical Cool Care System) while receiving care on a ra-

diant warmer servo-controlled to the infants abdominal skin tem-

perature adjusted to maintain the rectal temperature at 34 - 35C

for 72 hours. One hundred and sixteen infants received standard

care on the radiant warmer servo-controlled to infants abdominal

skin temperature that was adjusted to maintain rectal tempera-

ture at 36.8 - 37.2C (Gluckman 2005). This study did not report

withdrawal of care in deaths. The 18 month neurodevelopmental




10/58

assessment (neurological examination, visual and auditory assess-

ment andBSID) wasperformed by certified staff and developmen-tal psychologists blinded to treatment group assignment. Severe

neurodevelopmental disability was defined byGluckman 2005 as

gross motor function (GMF) level 3 - 5, Bayley MDI < 70, or

bilateral cortical visual impairment. In this review, we subtracted

died from died or severe disability at 18 months as reported in

Table 3 ofGluckman 2005 to obtain major neurodevelopmental

disability.

Shankaran 2005, forthe NICHDNeonatal Research Network,re-

ported mortality and moderate/severe disability at 18 - 22 months

in 205/208 (98.5%) term and near-term infants less than 6 hours

of age with either (a) pH < 7.0 or base deficit > 16 mmol/L on

cord blood or blood gas within one hour of birth, or (b) if no

blood gas or if pH 7.01 - 7.15 mmol/L or base deficit 10 - 15.9then additional criteria required: acute perinatal event(late or vari-

able decelerations, cord prolapse, cord rupture, uterine rupture,

maternal trauma, haemorrhage or cardiorespiratory arrest) AND

either 10 minute Apgar score < 5 or assisted ventilation initiated

at birth and continued for at least 10 minutes and encephalopa-

thy (on standardized neurologic examination by a certified exam-

iner) or clinical seizures. Infants were excluded if they were unable

to be enrolled by six hours of age, had major congenital abnor-

malities or growth restriction (birth weight < 1800 grams), had

consent refused by parent or neonatologist, or were moribund.

One hundred and two infants were placed on a pre-cooled in-

fant blanket (Blanketrol II Hyper-Hypothermia System, Cincin-

nati Sub-Zero) servo-controlled to oesophageal temperature of 33- 34C for 72 hours; a second blanket was included in the cool-

ing system to diminish oesophageal temperature variability. One

hundred and six infants received standard care with skin temper-

ature servo-controlled to abdominal skin temperature 36.5 - 37C

(Shankaran 2005). Withdrawal of care preceded death in 39 of

the 62 deaths (12/24 cooled and 27/38 standard care). Trained

developmental examiners blinded to treatment group assignment

performed the 18 - 22 month neurodevelopmental assessment of

growth, vision, hearing, neurologic examination and development

using the BSID. Severe disability was defined byShankaran 2005

as any of the following: GMF level 3 - 5, Bayley MDI


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to 12 months was incomplete (81.5%) in one trial (Eicher 2005).

Longer-term neurodevelopmental outcomes (18 - 22 months)were reported in 100% (Gunn 1998),93%(Gluckman 2005)and

98% (Shankaran 2005) of survivors, with masking of neurode-

velopmental outcome assessors to study group assignment (Gunn

1998; Eicher 2005; Gluckman 2005; Shankaran 2005). The qual-

ity of the neurodevelopmental outcome assessmentwas considered

to be high in three studies that followed survivors to at least 18

months of age (Gunn 1998; Gluckman 2005; Shankaran 2005)

andlower in thestudythat hadincompletefollow up to 12 months

(Eicher 2005).

Effects of interventions

Six hundred and thirty-eight near-term infants with moderate

or severe encephalopathy and evidence of intrapartum asphyxia

were enrolled in eight randomised controlled trials to determine

the effect of therapeutic hypothermia on mortality (Gunn 1998;

Shankaran 2002; ICE 2002;Akisu 2003; Eicher 2005; Gluckman

2005; Shankaran 2005; Lin 2006), short-term medical (Gunn

1998; Shankaran 2002; ICE 2002; Akisu 2003; Eicher 2005;

Gluckman 2005; Shankaran 2005) and longer-term neurodevel-

opmental outcomes (Gunn 1998; Eicher 2005; Gluckman 2005;

Shankaran 2005).

THERAPEUTIC HYPOTHERMIA VS. STANDARD CARE

(ALL INFANTS) (COMPARISON 01)

Death or major neurodevelopmental disability in survivorsassessed (Tables 01.01, 01.02):

Death or major neurodevelopmental disability in survivors

assessed by quality of follow-up (Table 01.01):

Data which permitted the assessment of the effect on this compos-

ite outcome were available from four trials (Gunn 1998; Eicher

2005; Gluckman 2005; Shankaran 2005). There was a total of

506 participants, of whom 287 either died or had major neurode-

velopmental disability at follow-up assessment. Two of the trials

(Shankaran 2005; Eicher 2005) found a significant reduction in

the incidence of death or major neurodevelopmental disability in

the hypothermia groups. Meta-analysis of all four trials found a

significant reduction in death or major neurodevelopmental dis-ability in survivors [typical RR 0.76 (95% CI 0.65, 0.89), typi-

cal RD -0.15 (95% CI -0.24, -0.07), NNT 7 (95% CI 4, 14)].

There was no evidence of heterogeneity (I squared 0%). In the

three trials with high quality follow-up (Gunn 1998; Gluckman

2005; Shankaran 2005), the reduction in death or major disability

was statistically significant [typical RR 0.79 (95% CI 0.67, 0.93),

typical RD -0.13 (95% CI -0.22, -0.04), NNT 8 (95% CI 4, 25)].

The effect was also significant in the one trial with lower quality

follow-up (Eicher 2005).

Data were missing for the primary outcome for this review, death

or major disability, in a few participants in three trials: Eicher

2005 (5 cooled, 8 control), Gluckman 2005 (8 cooled, 8 con-

trol), Shankaran 2005 (0 cooled, 3 control). After allowing for

uncertainty due to these missing outcome data (Gamble 2005),the reduction in the risk of death or major disability was main-

tained: uncertainty interval for risk difference -0.24, -0.04 (data

not shown).

Death or major disability in survivors assessed by method of

cooling (Table 01.02):

Meta-analysis of thetwo trialsthat used selective head coolingwith

mild systemic hypothermia (Gunn 1998; Gluckman 2005) failed

to show a statistically significant effect [typical RR 0.85 (95%

CI 0.69, 1.05), typical RD -0.09 (95% CI -0.21, 0.03)] . Meta-

analysis of the two trials (Eicher 2005; Shankaran 2005) that used

whole body cooling demonstrated a significant reduction in death

or disability in the hypothermia groups [typical RR 0.69 (95% CI

0.55, 0.86), typical RD -0.21 (95% CI -0.33, -0.09)]. There wasno evidence of heterogeneity of effect (I squared 0%).

Mortality by method of cooling (Table 01.03):

Eight trials reported on mortality (Gunn 1998; Shankaran 2002;

ICE 2002;Akisu 2003; Eicher 2005; Gluckman 2005; Shankaran

2005; Lin 2006). There were 638 infants and 185 deaths in total.

Only one of the trials (Shankaran 2005) found a statistically sig-

nificant effect, a reduction in mortality in the hypothermia group.

The meta-analysis of all eight trials demonstrated a significant re-

duction in mortality in the hypothermia groups [typical RR 0.74

(95% CI 0.58, 0.94), typical RD -0.09 (95% CI -0.16, -0.02),

NNT 11 (95% CI 6, 50)]. The effect was consistent across trials,

with no important heterogeneity (I squared 0%).

Meta-analysis of the four trials (Gunn 1998; Akisu 2003;Gluckman 2005; Lin 2006) that used selective head cooling with

mild systemic hypothermia did not show a statistically significant

effect on mortality [typical RR 0.83 (95% CI 0.59, 1.16), typical

RD -0.05 (95% CI -0.14, 0.04)]. However, meta-analysis of the

four trials that used whole body cooling (ICE 2002; Shankaran

2002; Eicher 2005; Shankaran 2005) demonstrated a significant

reduction in mortality in the hypothermia groups [typical RR 0.66

(95% CI 0.47, 0.93), typical RD -0.13 (95% CI -0.23, -0.02);

NNT 8 (95% CI 4, 50)]. This effect was consistent within this

group, with no important heterogeneity (I squared 0%).

Major neurodevelopmental disability (Tables 01.04 - 01.06):

Major neurodevelopmental disability by quality of follow-up

(Table 01.04):Four trials reported on neurodevelopmental disability (Gunn

1998; Eicher 2005; Gluckman 2005; Shankaran 2005). There

were 506 randomized infants with known outcomes, of whom

117 had major neurodevelopmental disability. The meta-analy-

sis failed to show a statistically significant effect [typical RR 0.79

(95% CI 0.57, 1.09), typical RD -0.05 (95% CI -0.13, 0.02)].

There was no evidence of heterogeneity of effect (I squared 0%).

Major neurodevelopmental disability in survivors assessed by

quality of follow-up (Table 01.05):

Four trials reported effect on this outcome (Gunn 1998; Eicher

2005; Gluckman 2005; Shankaran 2005). There was a total of




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336 survivors with neurodevelopmental follow-up, of whom 117

had major neurodevelopmental disability. Meta-analysis of all fourtrials demonstrated a significant reduction in major neurodevel-

opmental disability among survivors in the hypothermia groups

[typical RR 0.68 (95% CI 0.51, 0.92), typical RD -0.13 (95% CI

-0.23, -0.03)]. There was mild heterogeneity of treatment effect (I

squared 9%). Among the three trials with high quality follow-up

(Gunn 1998; Gluckman 2005; Shankaran 2005), there was a sig-

nificant reduction in major neurodevelopmental disability in the

hypothermia groups [typical RR 0.73 (95% CI 0.53, 0.99), RD

-0.11 (95% CI -0.22, -0.01)]. In the one trial with lower quality

follow-up (Eicher 2005) there was a also significant reduction in

major disability in the hypothermia group.

Major neurodevelopmental disability in survivors assessed by

method of cooling (Table 01.06):Meta-analysis ofthe twotrials that used selective headcooling with


to show a statistically significant effect [typical RR 0.77 (95%

CI 0.51, 1.17), typical RD -0.09 (95% CI -0.24, 0.05)]. How-

ever, meta-analysis of the two trials that used whole body cooling

(Eicher 2005; Shankaran 2005) demonstrated a significant reduc-

tion in major neurodevelopmental disability among survivors in

the hypothermia groups [typical RR 0.60 (95% CI 0.40, 0.92),

typical RD -0.17 (95% CI -0.31, -0.03)]. There was mild hetero-

geneity of treatment effect in these two trials (I squared 16%).

Cerebral palsy in survivors assessed by method of cooling (Ta-

ble 01.07):

Three trials reported effect on this outcome (Gunn 1998;Gluckman 2005; Shankaran 2005). There was a total of 306 sur-

vivors, of whom 90 had cerebral palsy. Meta-analysis of the three

trials showed no significant effectof hypothermiaon cerebral palsy

[typical RR 0.74 (95% CI 0.52, 1.05), typical RD -0.09 (95% CI

-0.19, 0.01)].

Neuromotor delay in survivors assessed (Table 01.08-01.10):

Four trials reported effect on neuromotor outcome (Gunn 1998;

Eicher 2005; Gluckman 2005; Shankaran 2005) . There was a

total of 311 survivors, of whom 111 had neuromotor delay on

the PDI more than 2 SD below the mean using the BSID. Meta-

analysis of the four trials demonstrated a reduction in neuromotor

delay on PDI in the hypothermia groups that was of borderline

statistical significance [typical RR 0.73 (95% CI 0.53, 1.00), typ-ical RD -0.10 (95% CI -0.21, 0.00)]. There was no evidence of

heterogeneity of effect (I squared 0%). Neuromotor delay in sur-

vivors assessed was not significant when only high quality studies

were analysed [typical RR 0.79 (95% CI 0.56, 1.11), typical RD

-0.08 (95% CI -0.18, 0.03)].(TABLE 01.08).

Meta-analysis of the two trials that used selective head cooling

with mild systemic hypothermia (Gunn 1998; Gluckman 2005)

failed to showa statistically significant effect[typical RR 0.81(95%

CI 0.51, 1.29), typical RD -0.07 (95%CI -0.22, 0.08)]. Also,

meta-analysis of the two trials that used whole body cooling (

Eicher 2005; Shankaran 2005) did not demonstrate a statistically

significant reduction in neuromotor disability in the hypothermia

groups [typical RR 0.66 (95% CI 0.42, 1.02), typical RD -0.14(95% CI -0.28, 0.01)]. Therewas mild heterogeneity of treatment

effect (I squared 8%) (TABLE 01.09).

Two trials comprising 158 survivors reported effect on neuromo-

tor delay in survivors assessed on the PDI using the BSID (Gunn

1998; Shankaran 2005). Meta-analysis demonstrated no signifi-

cant difference in mean PDI in the hypothermic groups [WMD

0.76 (95% CI -5.15, 6.68)] (TABLE 01.10).

Developmental delay in survivors assessed (Table 01.11-

01.13):

Four trials reported developmental delay or intellectual impair-

ment (Gunn 1998; Eicher 2005; Gluckman 2005; Shankaran

2005). There was a total of 319 survivors, of whom 100 had de-velopmental delay on MDI more than 2 SD below the mean us-

ing the BSID. Meta-analysis of the four trials failed to show a

statistically significant effect in the hypothermia groups [typical

RR 0.74 (95% CI 0.53, 1.02), typical RD -0.10 (95% CI -0.20,

0.01)]. Meta-analysis of the three high quality trials (Gunn 1998;

Gluckman 2005; Shankaran 2005) also failed to show a statisti-

cally significant effect in cooled infants [RR 0.76 (95% CI 0.54,

1.06), RD -0.09 (95% CI -0.20, 0.02)] (TABLE 01.11).

Meta-analysis of thetwo trialsthat used selective head coolingwith


to show a statistically significant effect [typical RR 0.86 (95% CI

0.54, 1.36), typical RD -0.05 (95% CI -0.19, 0.10)]. Meta-anal-

ysis of the two trials that used whole body cooling (Eicher 2005;Shankaran 2005) demonstrated a reduction in developmental de-

lay on MDI in the hypothermia groups that was of borderline sta-

tistical significance [typical RR 0.64 (95% CI 0.41, 1.00), typical

RD -0.14 (95% CI -0.28, 0.00)] (TABLE 01.12).

Two trials reported the effect of hypothermia on mental develop-

ment in 158 survivors assessed on MDI using the BSID (Gunn

1998; Shankaran 2005). Meta-analysis demonstrated no signifi-

cant difference in mean MDI in the hypothermic groups [WMD

1.93 (95% CI -4.16, 8.03)] (TABLE 01.13).

Blindness in survivors assessed (Table 01.14):

Four trials reported effect of hypothermia on this visual outcome

(Gunn 1998; Eicher 2005; Gluckman 2005; Shankaran 2005).

There was a total of 328 survivors, of whom 35 were legally blind.Meta-analysis of the four trials showed no significant effect of

hypothermia on the visual outcome of blindness [typical RR 0.57

(95% CI 0.30, 1.08), typical RD -0.06 (95% CI -0.13, 0.01)].

Sensorineural hearing loss requiring amplification (Table

01.15):

Four studies reported effecton thisauditoryoutcome(Gunn 1998;

Eicher 2005; Gluckman 2005; Shankaran 2005). There was a

total of 314 survivors, of whom 17 had sensorineural hearing loss

requiring amplification. Meta-analysisshowed no significant effect

of hypothermia on aided sensorineural hearing loss [typical RR

0.93 (95% CI0.37,2.34),typical RD0.00 (95% CI -0.06,0.05)].




13/58

Cardiovascular adverse effects (Table 01.16-01.18):Five trials reported effect on heart rate (Gunn 1998; Akisu 2003;

Eicher 2005; Gluckman 2005; Shankaran 2005).There was a total

of 552 infants, of whom 26 had a sinus bradycardia below 80/

minute. Meta-analysis of the five trials demonstrated significantly

increased sinus bradycardia in hypothermia groups [typical RR

5.96 (95% CI 2.15, 16.49), typical RD 0.07 (95% CI 0.04, 0.11)]

(TABLE 01.16).

Five trials reported the effect of hypothermia on the need for

blood pressure support with inotropes (Gunn 1998; ICE 2002;

Shankaran 2002; Gluckman 2005; Shankaran 2005). There was

a total of 505 infants, of whom 266 required inotrope support

for hypotension. Meta-analysis of the five trials demonstrated an

increase in hypotension treated with inotropes in hypothermiagroups that was of borderline significance [typical RR 1.17 (95%

CI 1.00, 1.38), typical RD 0.08 (0.00, 0.17)] (TABLE 01.17).

Six trials reported effect of hypothermia on cardiac arrhythmia

requiring medical intervention and/or cessation of cooling (Gunn

1998; ICE 2002; Akisu 2003; Eicher 2005; Gluckman 2005;

Shankaran 2005). There was a total of 569 infants, of whom2 had

an arrhythmiarequiring medical intervention. Meta-analysis of the

six trials failed to demonstrate a significant effect of hypothermia

on arrhythmiarequiring medical treatmentin hypothermic groups

[typical RR 1.04 (95% CI 0.07, 16.39), typical RD 0.00 (-0.02,

0.02)] (TABLE 01.18).

Haematological adverse effects (Table 01.19-0.22):

Three trials reported the effect of hypothermia on anaemia re-quiring blood transfusion (Gunn 1998; Eicher 2005; Gluckman

2005). There was a total of 322 infants, of whom 39 were trans-

fused for anaemia. Meta-analysis of the three trials failed to show

significant effect of hypothermia on anaemia requiring blood

transfusion [typical RR 1.16 (95% CI 0.67, 2.04), typical RD

0.02 (95% CI -0.05, 0.09)] (TABLE 01.19).

Two trials reported the effect of hypothermia on white cell count

(Gunn 1998; Gluckman 2005). There was a total of 254 infants,

of whom 6 had leukopaenia with a white cell count below 5 x

109/L. Meta-analysis of the two trials failed to show significant

effect of hypothermia on the incidence of leukopaenia [typical RR

0.97 (95% CI 0.22, 4.33), typical RD 0.00 (95% CI -0.04, 0.04)]

(TABLE 01.20).Four trials reported the effect of hypothermia on platelet count

(Gunn 1998; Eicher 2005; Gluckman 2005; Shankaran 2005).

There was a total of 531 infants, of whom 124 were thrombocy-

topaenic with platelet count below 150 x 109/L. Meta-analysis of

the four trials showed statistically significantly increased throm-

bocytopaenia in the hypothermic groups [typical RR 1.55 (95%

CI 1.14, 2.11), typical RD 0.09 (95% CI 0.03, 0.15)] (TABLE

01.21).

Four trials reported the effect of hypothermia on coagulopathy

resulting in major thrombosis or haemorrhage (Gunn 1998; ICE

2002; Gluckman 2005; Shankaran 2005).Therewasatotalof486

infants, of whom 14 had severe coagulopathy. Meta-analysis of the

four trials failed to show significant effect on severe coagulopathyin cooled infants [typical RR 0.83 (95% CI 0.31, 2.24), typical

RD -0.01 (95% CI -0.03, 0.02)] (TABLE 01.22).

Metabolic adverse effects (Table 01.23-0.24):

Four trials reported the effect of hypothermia on glucose home-

ostasis (Gunn 1998, Akisu 2003; Gluckman 2005; Shankaran

2005). There was a total of 490 infants, of whom 73 were hypo-

glycaemic with a blood glucose below 2.6 mmol/L. Meta-analysis

of the four trials failed to show significant hypoglycaemia in hy-

pothermic groups [typical RR 0.83 (95% CI 0.54, 1.27), typical

RD -0.03 (95% CI -0.09, 0.03)] (TABLE 01.23).

Threetrials reported the effectof hypothermiaon serumpotassium

(Gunn 1998; Eicher 2005; Gluckman 2005). There was a total

of 323 infants, of whom 175 had hypokalaemia with a serumpotassium below 3.5 mmol/L. Meta-analysis of the three trials

showed no statistically significant difference in the incidence of

hypokalaemia in cooled infants [typical RR 1.03 (95% CI 0.85,

1.25), typical RD 0.02 (95% CI -0.09, 0.12)] (TABLE 01.24).

Renal impairment (Table 01.25):

Five trials reported the effect of hypothermia on urine out-

put (Gunn 1998; ICE 2002; Shankaran 2002; Gluckman 2005;

Shankaran 2005). There was a total of 505 infants, of whom 147

had oliguria with urine output below 1 mL/kg/hour. Meta-analy-

sis of the five trials showed no statistically significant difference in

rate of oliguria in cooled infants [typical RR 0.81 (95% CI 0.59,

1.12), typical RD -0.05 (95% CI -0.12, 0.03)].

Sepsis (Table 01.26):Five trials reported the effect of hypothermia on sepsis (Gunn

1998; Akisu 2003; Eicher 2005; Gluckman 2005; Shankaran

2005). There were a total of 552 infants, of whom 28 had culture

proven sepsis. Meta-analysis of the five trials failed to show a sig-

nificant effect of hypothermia on sepsis [typical RR 0.86 (95% CI

0.42, 1.76), typical RD -0.01 (-0.04, 0.03)].

Short-term neurological outcomes (Table 01.27):

Five trials reported the effect of hypothermia on clinically recog-

nized seizures (Gunn 1998; ICE 2002; Shankaran 2002; Akisu

2003; Gluckman 2005). There were a total of 322 infants, of

whom 220 had clinically recognized seizures. Meta-analysis of five

trials failed to show a significant effect of therapeutic hypothermia

on the incidence of clinically recognized seizures [typical RR 0.96(95% CI 0.84, 1.10), typical RD -0.03 (95% CI -0.12, 0.07)].

Other short-term neurological outcomes have not been reported,

including MRI, standardised neurological assessment and days to

full sucking feeds.

In summary, there was a borderline significant negative effect of

hypothermia on the need for inotrope support and a significant

increase in thrombocytopaenia with a platelet count below 150 x

109/L. There was no significant effect of hypothermia on other

short term adverse outcomes or on neurological status as defined

by the incidence of clinically recognized seizures in the first three

days of life. Analysis of many secondary outcomes planned for




14/58

this review were unable to be performed because they were not

reported in the included trials. Many planned subgroup analyseson the basis of gestation, timing of commencement of cooling, as

well as the degree and duration of cooling and rewarming were

still unable to be performed because of lack of eligible data.


(INFANTS WITH SEVERE ENCEPHALOPATHY) (COM-

PARISON 02)

Death or major disability in survivors assessed (Table 02.01):

Three trials reported the effect of hypothermia on this composite

outcome (Gunn 1998; Gluckman 2005; Shankaran 2005). There

was a total of 153 infants with severe encephalopathy, of whom

122 died or survived with major neurodevelopmental disability.

Meta-analysis of the three trials found a significant reduction in

death or major neurodevelopmental disability in survivors [typicalRR 0.80 (95% CI 0.68, 0.94), typical RD -0.18 (95% CI -0.31,

-0.05), NNT 6 (95% CI 3, 20)].

Mortality (Table 02.02):

Three trials reported the effect of hypothermia on mortality in

infants withsevere encephalopathy (Gunn1998; Gluckman 2005;

Shankaran 2005). There was a total of 153 infants with severe

encephalopathy, of whom 82 died. One trial (Gluckman 2005)

found a significant reduction in the cooled group. Meta-analysis of

the three trialsfound a significant reduction in mortalityin infants

with severeencephalopathy [typical RR 0.72 (95% CI 0.56, 0.94),

typical RD -0.20 (95% CI -0.35, -0.04), NNT 5 (95% CI 3, 25)].

Major disability in survivors assessed (Table 02.03):

Three trials reported the effect of hypothermia on neurodevel-opmental disability in survivors assessed (Gunn 1998, Gluckman

2005; Shankaran 2005). There was no significant effect of cooling

on disability in the 62 survivors who had severe encephalopathy

[typical RR 0.69 (95% CI 0.42, 1.13); typical RD -0.19 (95% CI

-0.44, 0.07)].


(INFANTS WITH MODERATE ENCEPHALOPATHY)

(COMPARISON 03)

Death or major disability in survivors assessed (Table 03.01):

Three trials reported the effect of hypothermia on this composite

outcome (Gunn 1998; Gluckman 2005; Shankaran 2005). There

was a total of 278 infants with moderate encephalopathy, of whom124 died or survived with major neurodevelopmental disability.

Meta-analysis of the three trials found a reduction in death or ma-

jor neurodevelopmental disability in survivors that was of border-

line statistical significance [typical RR 0.76 (95% CI 0.58, 1.00),

typical RD -0.12 (95% CI -0.23, 0.00)].

Mortality (Table 03.02):

Three trials reported the effect of hypothermia on mortality in

infants with moderate encephalopathy (Gunn 1998; Gluckman

2005; Shankaran 2005). There was a total of 278 infants with

moderate encephalopathy, of whom 52 died. Meta-analysis of the

three trials failed to show a significant effect on mortality in cooled

infants with moderate encephalopathy [typical RR 0.79 (95% CI

0.49, 1.29), typical RD -0.04 (95% CI -0.14, 0.05)].Major disability in survivors assessed (Table 03.03):

Three trials reported the effect of hypothermia in infants with

moderate encephalopathy on neurodevelopmental disability in

survivors assessed (Gunn 1998; Gluckman 2005; Shankaran

2005). There were 226 survivors with moderate encephalopathy,

of whom 72 had major neurodevelopmental disability. Meta-anal-

ysis of the three trials did not demonstrate any significant effect

on disability among survivors who had moderate encephalopathy

[typical RR 0.71 (95% CI 0.48, 1.05); typical RD -0.11 (95% CI

-0.23, 0.01)].

D I S C U S S I O N

This systematic review demonstrates that therapeutic hypother-

mia for term newborn infants with moderate or severe hypoxic

ischaemic encephalopathy results in a reduction in the composite

outcome of mortality or long-term neurodevelopmental disability

to 18 months of age. This result is both statistically significant

and clinically important, with a relative risk reduction of 24%,

absolute risk reduction of 15% and NNT of 7. To prevent one

death or major disability, one would need to treat as many as 14

infants or as few as four infants. This reduction in death or ma-

jor disability remains significant in the subgroup analysis for se-

vere encephalopathy (NNT 6, as many as 20 infants or as few asthree infants), and is of borderline significance for moderate en-

cephalopathy. In the overall analysis, the effects on each compo-

nent contributing to the composite outcome (death, major neu-

rodevelopmental disability in survivors) are also statistically signif-

icant and clinically important. These results are consistent across

the four trials that measured the effect on death or major disability

(I squared 0%). Overall, the methodology of the included stud-

ies is strong. This is particularly true of the two largest studies

(Gluckman 2005; Shankaran 2005) that contributed most of the

weight to the pooled analysis.

Animportant outcome of this reviewis that cooling decreasesmor-

tality, without increasing major neurodevelopmental disability in

survivors. Among all treated infants, there is a significant reduc-

tion in mortality (analysis 01.03) with a statistically insignificant

trend towards a decrease in major disability (analysis 01.04). The

upper limit on the RD confidence interval shows that the most

pessimistic view would be that any increase in major disability

among a population of similar babies treated with hypothermia

is unlikely to be more than 2%. In addition, major neurodevel-

opmental disability is significantly reduced in survivors (analysis

01.05). Therefore, cooling reduces mortality and if an infant sur-

vives, also decreases his/her chance of major disability.

Several limitations of the available evidence should be noted. By

clinical necessity, the caretakers could not be blinded to the inter-




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vention. Even so, in each of the four trials that assessed the effect

of cooling on major neurodevelopmental disability, assessors ofneurodevelopment were blinded to treatment group assignment.

The effect of treatment group on mortality could be biased by the

unblinded intervention if it resulted in fewer decisions by caretak-

ers to withdraw intensive care in cooled babies. However, the find-

ing that major neurodevelopmental disability was not increased in

survivors who had been cooled does not support this speculation.

In the overall analyses, the number of infants studied is substantial;

the estimates of treatment effecton the primary outcome, death or

major neurodevelopmental disability, and on each component of

this composite outcome, were reasonably precise. However, these

estimates of treatment effect were less precise in subgroup analysesbasedon degree of encephalopathy, method of cooling, and quality

of follow-up. The better method of cooling may remain uncertain

until selective head cooling and whole body cooling are directly

compared in clinical trials.

Reporting of many of the secondary outcomes specified in our

original protocol is not adequate to assess adverse outcomes or

safety. More cooled infants had significant thrombocytopaenia.

The increased treatment of hypotension with inotropes in cooled

infants was of borderline significance.

Cautious application of the results of this meta-analysis is rec-ommended. Trials contributing participants to this meta-analysis

were conducted within strict protocols and often at centres of ex-

cellence with considerable experience in therapeutic hypothermia.

There are at least three ongoing randomised controlled trials of

whole body cooling in term infants with HIE (n = 672) (ICE;

nnn-Hypothermia; TOBY) andone awaiting assessment (n = 157)

(Shao 2006). The results of this review are based on 638 infants,

fewer than half the number of patients known to have been ran-

domized into eligible trials. Incorporation of the results of these

trials comprising an additional 829 infants into future updates of

this review could alter the present results and conclusions.

A U T H O R S C O N C L U S I O N S

Implications for practice

There is evidence from the eight randomised controlled trials (n =

638) included in this systematic review that therapeutic hypother-

mia is beneficial to term newborns with hypoxic ischaemic en-

cephalopathy. Deathor major disability, mortality and in neurode-

velopmental disability in survivors are all reduced. Importantly,

mortality is reduced without increasing major disability in sur-

vivors. While there is also some evidence of harm from therapeutic

hypothermia, increased thrombocytopaenia and hypotension, the

benefits of cooling on survival and neurodevelopment outweigh

these short-term adverse effects.

It is important to note that this review comprises an analysis basedon less than half of all infants currently known to be randomised

into eligible trials of cooling. Careful follow-up of all infants from

another four ongoing randomised trials (n = 829) and incorpo-

ration of data will clarify the effectiveness and safety of cooling.

This additional data could potentially alter the results and modify

these conclusions.

Implications for research

Further well designed and executed studies withappropriate power

are required to determine the most appropriate method of provid-

ingtherapeutic hypothermia. These studies should comparewhole

body with selective head cooling with mild systemic hypothermia,

and evaluate simpler methods of cooling, earlier initiation of cool-

ing, the most appropriate method and duration of rewarming and

hypothermia combined with adjunctive therapies.

A C K N O W L E D G E M E N T S

We thank all the authors of the included studies, particularly

Malcolm Battin, Dorothy Jenkins, Alistair Gunn and Seetha

Shankaran for the NICHD Neonatal Research Network who clar-

ified existing data and provided us with additional information.

R E F E R E N C E S

References to studies included in this review

Akisu 2003 {published data only}

Akisu M, Huseyinov A, Yalaz M, Cetin H, Kultursay N.

Selective head cooling with hypothermia suppresses the

generation of platelet-activating factor in cerebrospinal fluid

of newborn infants with perinatal asphyxia. Prostaglandins,

Leokotrienes and Essential Fatty Acids2003;69:4550.

Eicher 2005 {published and unpublished data} Eicher D, Wagner C, Katikaneni L, Hulsey T, Bass T,

Kaufman D, et al.Moderate hypothermia in neonatal

encephalopathy: Efficacy outcomes. Pediatric Neurology

2005;32:117.

Eicher D, Wagner C, Katikaneni L, Hulsey T, Bass T,

Kaufman D, et al.Moderate hypothermia in neonatal

encephalopathy: safety outcomes. Pediatric Neurology2005;

32:1824.

Gluckman 2005 {published and unpublished data} Gluckman P, Wyatt J, Azzopardi D, Ballard R, Edwards D,

Ferriero D, et al.Selective head cooling with mild systemic




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hypothermia after neonatal encephalopathy: multicentre

randomised trial. Lancet2005;365:66370.Wyatt J, Gluckman P, Liu P, Azzopardi D, Ballard R,

Edwards D, et al.Determinants of outcomes after head

cooling for neonatal encephalopathy. Pediatrics2007;119:

91221.

Gunn 1998 {published and unpublished data}

Battin MR, Dezoete JA, Gunn TR, Gluckman PD, Gunn

AJ. Neurodevelopmental outcome of infants treated with

head cooling and mild hypothermia after perinatal asphyxia.

Pediatrics2001;107:4804.

Battin MR, Penrice J, Gunn TR, Gunn AJ. Treatment

of term infants with head cooling and mild systemic

hypothermia (35C and 34.5C) after perinatal asphyxia.


Gunn AJ, Gluckman PD, Gunn TR. Selective headcooling in newborn infants after perinatal asphyxia: A safety

study. Pediatrics1998;102:88592.

ICE 2002 {published and unpublished data}

Inder T, Hunt R, Morley C, Coleman L, Stewart M, Doyle

L, Jacobs S. Randomized trial of systemic hypothermia

selectively protects the cortex on MRI in term hypoxic-

ischemic encephalopathy. Journal of Pediatrics2004;145:

8357. Jacobs S, Stewart M, Inder T, Doyle L, Morley C.

Feasibility of a pragmatic randomised controlled trial of

whole body cooling for term newborns with hypoxic-

ischaemic encephalopathy. Hot Topics in Neonatology.

2002.

Lin 2006 {published data only}

Lin Z, Yu H, Lin J, Chen S, Liang Z, Zhang Z. Mild

hypothermia via selective head cooling as neuroprotective

therapy in term neonates with perinatal asphyxia: an

experience from a single neonatal intensive care unit.

Journal of Perinatology2006;26:1804.

Shankaran 2002 {published data only}

Shankaran S, Laptook A, Wright LL, Ehrenkranz RA,

Donovan EF, Fanaroff AA, et al.Whole-body hypothermia

for neonatal encephalopathy: animal observations as a basis

for a randomized, controlled pilot study in term infants.


Shankaran 2005 {published and unpublished data}

Shankaran S, Laptook A, Ehrenkranz R, Tyson J, McDonaldS, Donovan E, et al.Whole-body hypothermia for neonates

with hypoxic-ischemic encephalopathy. New England

Journal of Medicine2005;353:157484.

References to studies excluded from this review

Azzopardi 2000 {published data only}

Azzopardi D, Robertson NJ, Rutherford MA, Rampling M,

Edwards AD. Pilot study of treatment with whole body

hypothermia for neonatal encephalopathy. Pediatrics2000;

106:68494.

Compagnoni 2002 {published data only}

Compagnoni G, Pogliani L, Lista G, Castoldi F, Fontana

P, Mosca F. Hypothermia reduces neurological damage in

asphyxiated newborn infants. Biology of the Neonate 2002;

82:2227.Debillon 2003 {published data only}

Debillon T, Daoud P, Durand P, Cantagrel S, Jouvet P,

Saizou C, Zupan V. Whole-body cooling after perinatal

asphyxia: a pilot study in term neonates. Developmental

Medicine and Child Neurology2003;45:1723.

Horn 2006 {published data only}

Horn AR, Woods DL, Thompson C, Eis I, Kroon

M. Selective cerebral hypothermia for post-hypoxic

neuroprotection in neonates using a solid ice cap. South

African Medical Journal2006;96:97681.

Kilani 2002 {published data only}

Kilani RA. The safety and practicality of selective head

cooling in asphyxiated human newborn infants, aretrospective study. Lebanese Medical Journal2002;50:

1722.

Lista 2004 {published data only}

Lista G, Pogliani P, Fontana P, Castoldi F, Compagnoni

G. Cardiovascular and respiratory status in mechanically

ventilated asphyxiated term infants: comparison between

hypothermic and control group. Acta Bio Medica Ateneo

Parmense2004;75:10713.

Simbruner 1999 {published data only}

Simbruner G, Haberl C, Harrison V, Linley L, Willeitner

AE. Induced brain hypothermia in asphyxiated human

newborn infants: a retrospective chart analysis of

physiological and adverse effects. Intensive Care Medicine

1999;25:11117.Thoresen 2000 {published data only}

Thoresen M, Whitelaw A. Cardiovascular changes during

mild therapeutic hypothermia and rewarming in infants

with hypoxic-ischemic encephalopathy. Pediatrics2000;

106:929.

Zhou 2002 {published data only} Zhou WH, Shao XM, Cao Y, Chen C, Zhang XD. Safety

study of hypothermia for treatment of hypoxic-ischemic

brain damage in term neonates. Acta Pharmacologica Sinica

2002;23:648.

Zhou WH, Shao XM, Zhang XD, Chen C, Huang GY.

Effects of hypothermia on cardiac function in neonates with

asphyxia [Chinese]. Zhonghua Erke Zazhi (Chinese Journal

of Pediatrics) 2003;41:4602.

References to studies awaiting assessment

Shao 2006 {unpublished data only}

Shao XM, Zhou WH. Efficacy and safety of selective

head cooling with mild systemic hypothermia after

neonatal hypoxic ischemic encephalopathy. Hot Topics in

Neonatology. 2006.

References to ongoing studies

ICE {unpublished data only}

Jacobs SE, Stewart M, Inder TE, Doyle LW, Morley C.

A randomised controlled trial of whole body cooling




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on the outcome of term babies with hypoxic ischaemic

encephalopathy.

nnn-Hypothermia {unpublished data only}

Simbruner G. Induced systemic hypothermia in asphyxiated

newborn infants: a randomized, controlled, multicenter

study.

TOBY {unpublished data only}

Azzopardi, D. Whole body hypothermia for the treatment

of perinatal asphyxial encephalopathy.

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Badawi N, Kurinczuk JJ, Keogh JM, Alessandri LM,

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Badawi, Kurinczuk JJ, Keogh JM, Alessandri LM,

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Battin 2001

Battin MR, Dezoete JA, Gunn TR, Gluckman PD, Gunn

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Battin 2003

Battin MR, Penrice J, Gunn TR, Gunn AJ. Treatment

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